1. Field of the Invention
The invention relates to a station-selecting device for a radio receiver.
2. Description of the Prior Art
In order to select stations, it has been the usual practice to make use of a capacitor having a capacitance which depends on the position of a moving element such as a metallic strip. This position, and therefore the tuning frequency or in other words the selected station, can be modified by means of a control knob which produces action on said moving element of the capacitor or like tuning device by means of a mechanical linkage. Said moving element is capable of moving only between two end positions, stops being provided for limiting its travel.
In order to prevent any damage to the mechanical linkage between the control knob and the moving element, provision is usually made for means whereby the rotation of the actuating knob is permitted to continue when the moving element has reached the end of travel. The means just mentioned utilize a coefficient of friction which is of sufficiently high value to permit motion transmission but remains of sufficiently low value to permit only sliding motion (without driving in rotation) when the moving element is at the end of travel.
In known devices, friction is set up either between a shaft and a string or between a shaft and the periphery of a wheel. Selecting devices of this type are relatively delicate or fail to offer sufficient reliability to meet current requirements.